A novel UHPLC-MS/MS method for the determination of three selenoamino acids in organic selenium supplements and dynamic monitoring in human urine after consumption

Selenium (Se) is a vital trace element for mammals, but excessive intake can lead to selenium poisoning. To manage Se intake properly, this study developed a novel method using ultra-high performance liquid chromatography–tandem mass spectrometry (UHPLC-MS/MS). This technique allows the simultaneous detection of three selenoamino acids in supplements. The three selenoamino acids were fully separated within 3 min. The method demonstrated excellent linearity (R² ≥ 0.9993), high sensitivity (detection limits were 2.49–2.92 fmol), and good precision (intraday and interday precision ranged from 2.87 to 13.54%). This study applied this method to analyze the content of selenoamino acids in organic selenium supplements from various sources and to dynamically monitor their absorption and excretion in the body after consumption. The novel approach offers a new strategy for the quality control of selenium-containing supplements and for studying selenium absorption and metabolism.